Creating Random Dates in ColdFusion: RandDateRange( dtFrom, dtTo )

By Ben Nadel

Published 2006-07-07 in ColdFusion — Comments (1)

Someone was just asking me how to create a random date in ColdFusion. More specifically, how to create a random date between two dates. The solutions for this is quite simple once you understand it. I have created a method named RandDateRange(). This method functions similar to RandRange( intFrom, intTo ) and actually uses that method under the hood. If you abstract generating a random date between two given dates, it comes down to picking a random point in time. We can create this random point by adding a random time span to the "From Date", making sure, of course, that this random time span does not give us a date past the desired "To Date".

The beauty of time spans in ColdFusion is that they can be represented as a single floating point number. This puts us in the perfect position to use RandRange() to create random time spans. To make sure that we do not create too large a timespan, our bottom range parameter will be zero and our top range parameter will be the difference in seconds between the two out lier dates. Therefore, if we get a random second value and add it to the "From Date", we know we can never go past the "To Date."

  
          <cffunction name="RandDateRange" access="public" returntype="date" output="false"
        
          	hint="This returns a random date between the two given dates (inclusive).">
        
          	<!--- Define arguments. --->
        
          	<cfargument name="FromDate" type="date" required="true" />
        
          	<cfargument name="ToDate" type="date" required="true" />
        
          	<cfscript>
        
          		// Define the local scope.
        
          		var LOCAL = StructNew();
        
          		// Get the difference in seconds between the two dates.
        
          		LOCAL.TimeDifference = DateDiff( 
        
          			"s", 
        
          			ARGUMENTS.FromDate, 
        
          			ARGUMENTS.ToDate 
        
          			);
        
          		// Create a random time increment based on the second difference. 
        
          		// The time span object is a representation of time-length in 
        
          		// terms of a single floating-point number.
        
          		LOCAL.TimeIncrement = CreateTimeSpan(
        
          			0, // Days
        
          			0, // Hours
        
          			0, // Minutes
        
          			RandRange( // Seconds
        
          				// Our smallest possible time increment.
        
          				0,
        
          				// Our largest possible time increment that will not 
        
          				// put us past the ToDate.
        
          				LOCAL.TimeDifference
        
          				)
        
          			);
        
          		// Get a new random date based on the FromDate and the random
        
          		// time span.
        
          		LOCAL.RandomDate = (ARGUMENTS.FromDate + LOCAL.TimeIncrement);
        
          		// This random date now is formatted like a TimeSpan object, 
        
          		// meaning that it is in the form of one floating point number.
        
          		return( LOCAL.RandomDate );
        
          	</cfscript>
        
          </cffunction>

view raw code-1.cfm hosted with ❤ by GitHub

Now to test it out. For the from and to dates, let's pick Now and one month from Now.

From: 2006-07-07
To: 2006-08-07

Now, get a random date between those to:

Random: 38931.4080093

As you can see above, the random date is in Time Span format (represented as a single floating point number). In order to fix that, all we have to do is run a date format on it. Now, keep in mind that ColdFusion still treats that as a valid date. You only need to change the formatting on it for display. You can add, diff, subtract all you want on the server side and its all good.

Formatted: 2006-08-02

Want to use code from this post? Check out the license.

Short link: https://bennadel.com/121

Reader Comments

Shaun Jan 8, 2014 at 4:59 AM

4 Comments

Nice!

Thanks for this, nice, tightly coded function that worked straight off the page. Integrated into a site in five minutes. You sire, are a champ.

Thanks
Shaun

Oh my chickens, this post is old!

Hit me up on Twitter if you want to discuss it further.

	<cffunction name="RandDateRange" access="public" returntype="date" output="false"
	hint="This returns a random date between the two given dates (inclusive).">

	<!--- Define arguments. --->
	<cfargument name="FromDate" type="date" required="true" />
	<cfargument name="ToDate" type="date" required="true" />

	<cfscript>

	// Define the local scope.
	var LOCAL = StructNew();

	// Get the difference in seconds between the two dates.
	LOCAL.TimeDifference = DateDiff(
	"s",
	ARGUMENTS.FromDate,
	ARGUMENTS.ToDate
	);

	// Create a random time increment based on the second difference.
	// The time span object is a representation of time-length in
	// terms of a single floating-point number.
	LOCAL.TimeIncrement = CreateTimeSpan(
	0, // Days
	0, // Hours
	0, // Minutes
	RandRange( // Seconds
	// Our smallest possible time increment.
	0,

	// Our largest possible time increment that will not
	// put us past the ToDate.
	LOCAL.TimeDifference
	)
	);

	// Get a new random date based on the FromDate and the random
	// time span.
	LOCAL.RandomDate = (ARGUMENTS.FromDate + LOCAL.TimeIncrement);

	// This random date now is formatted like a TimeSpan object,
	// meaning that it is in the form of one floating point number.
	return( LOCAL.RandomDate );

	</cfscript>
	</cffunction>